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DNA REPLICATION, CHROMOSOMES & THE CELL CYCLE

DNA REPLICATION, CHROMOSOMES & THE CELL CYCLE. SB2b. Explain the role of DNA in storing and transmitting cellular information.

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DNA REPLICATION, CHROMOSOMES & THE CELL CYCLE

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  1. DNA REPLICATION, CHROMOSOMES & THE CELL CYCLE SB2b. Explain the role of DNA in storing and transmitting cellular information. SB2d. Describe the relationships between changes in DNA and potential appearance of new traits including alterations during replication (insertions, deletions, substitutions) and mutagenic factors that can alter DNA (high energy radiation (x-rays and ultraviolet) & chemicals). SB2e. Compare the advantages of sexual reproduction and asexual reproduction in different situations.

  2. CELL REPRODUCTION • Asexual Reproduction • No sperm or egg are used • Newly produced cells are genetically identical to parent cell- clones • If it occurs in… • human body cells (like the skin)- called mitosis • single-celled organisms like bacteria or protists- called binary fission • simple animals (like sponge)- called budding • Sexual Reproduction • Sperm and egg are produced & fused • Newly produced cells are genetically different from each other and the parent cell. • This creates genetic diversity • If it occurs in • human body cells- called meiosis • Single-celled organisms like bacteria or protists- called conjugation.

  3. DNA REPLICATION Before cell can reproduce- the DNA must replicate.

  4. What is Replication? • Process by which DNA makes a copy of itself. • Copy needed for cell reproduction.

  5. Why is replication necessary? • So every new cell has an exact copy of original DNA strand.

  6. What are the steps of replication? • DNA untwists and DNA helicase enzyme helps it “unzip” into two separate strands. • Free nucleotides floating in the nucleus join onto strands to form 2 new strands of DNA. • Two complete strands will result, these will be exact copies of each other. • Each resulting strands has one new half of DNA and one old half of DNA.

  7. CHROMOSOMES After DNA replicates it becomes chromosomes…

  8. What are chromosomes? • Carriers of genetic material found in nucleus • Basically it is coiled up DNA • Chromosomes contain thousands of GENES which code for thousands of PROTEINS and are made up of millions of NITROGEN BASE PAIRS.

  9. What are the components of a chromosome? • Chromatin- long, thin strands of DNA • Chromosome - coiled up strands of chromatin. Forms an “X” like structure • 2 Sister Chromatids- each piece of a chromosome • Centromere- spot that holds each sister chromatid together.

  10. How many chromosomes are in human cells? • 46 in somatic (body) cells- like skin, muscle. • 23 in gametes (sex cells- like sperm & egg).

  11. THE CELL CYCLE After DNA replicates and is formed into chromosomes, the cell can go through the process of dividing.

  12. What is the cell cycle? • Sequence of growth and division in the cell

  13. INTERPHASE • Nucleus is intact. • Nucleolus is present. • Chromatin is loosely contained in nucleus. • Chromatin replicates. • Longest phase of the cell cycle

  14. PROPHASE • Longest phase of mitosis • Chromatin coils into chromosomes • The nucleus & nucleolus disappear • Centrioles form and move to opposite poles of cell • Spindle fibers form from centrioles and begin to cross cell

  15. METAPHASE • Chromosomes line up in the middle of the cell • Spindle now forms across the cell • Meta = “middle”

  16. ANAPHASE • Spindle fibers begin to shorten/break down • This pulls chromosomes apart • Now the chromosome halves are referred to as chromatids • Ana = “away”

  17. TELOPHASE • Chromatids reach poles • Chromosomes unwind into chromatin • Spindle fibers break down • Nucleolus and nuclei reform • Plasma membrane begins to cleave (pinch in)

  18. What is Cytokinesis?Division of cytoplasm How is cytokinesis different in plants and animals? • animal cells: cell membrane cleaves until two daughter cells are formed • plant cells: cell plate forms in center of cell and splits cells

  19. I- INTERPHASE P- PROPHASE M- METAPHASE A- ANAPHASE T- TELOPHASE I-P-M-A-T

  20. CANCER & THE CELL CYCLE Cancer is basically a disease of mitosis.

  21. What controls the division of cells? • Normal cells will grow until they touch another cell. • This is controlled by protein growth factors.

  22. What happens when division of cells is uncontrolled? • Cancer occurs when a normal cell is transformed into a cancer cell and the protein growth factors are mutated. • Now the cells grow on top of each other and form tumors. • Cancer cells grow until they run out of food

  23. What is the difference between benign and malignant tumors? • Masses of cancer tissue are called tumors • Benign- never leave original site • Malignant- abnormal mass of cancer cells; can metastasis or spread to other areas.

  24. What causes cancer? • Thought to be caused by changes in genes controlling mitosis. • Some cancers caused by viruses or are genetic • DNA can be mutated by chemicals in • Tobacco smoke • Pollution • UV radiation

  25. How is cancer treated? • Some chemical drugs stop DNA replication so no new cancer cells can form. • Vincristine & Taxol (both natural products of plants) block spindle fiber formation so mitosis is blocked- no mitosis, no new cancer cells!

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